Polysaccharides From Fermented <i>Cordyceps</i> Mycelium: In‐Depth Structural Characterization by Partial Acid Hydrolysis, Methylation and NMR Spectroscopy

ABSTRACT Polysaccharide is considered as one of the main bioactive constituents in Cordyceps sinensis ( C. sinensis ), one of the well‐known traditional Chinese medicines. In this study, novel polysaccharide fractions were isolated and fractionated from the mycelium of fermented Cordyceps by Sephadex G‐200 gel permeation chromatography and DEAE‐52 cellulose chromatography. The structure of the polysaccharide was investigated by high‐performance size‐exclusion chromatography (HPSEC), monosaccharide composition, partial acid hydrolysis, methylation analysis, and 1D/2D NMR spectroscopy. Three fractions with different molecular weight (CSP‐1 2.95 × 10 6 Da, CSP‐2 3.06 × 10 4 Da, CSP‐3 6.4 × 10 3 Da) isolated by gel permeation chromatography showing resemble structural properties, so the major and high‐purity fraction, CSP‐2, showing as both flexible and rod chain conformation in solution, was selected to further fractionate to obtain CSP2‐F0.05. The results showed that the polysaccharide in fermented Cordyceps mycelium was highly branched complex polysaccharide, mainly composed of galactose, glucose, and mannose in 42.27%:7.87%:39.86%. The backbone was mainly composed of α‐(1→6)‐Man p units with branching substituted at C‐2 and C‐4. Galactose and glucose were probably located at branches. This study contributed to add basic information in understanding the polysaccharide fractions in C. sinensis .